The present invention refers to a cartridge containing one serving of coffee powder for preparing a coffee beverage. Such cartridges are well known in the art in a plurality of embodiments, whereby particularly cartridges for preparing so-called espresso coffee beverage are in widespread use. The fundamental advantage of such cartridges may be seen in the fact that they are gas-tight, whereby the coffee powder is contained therein without oxygen that would impair the quality of the coffee powder during storage of the cartridge. Thus, the coffee powder contained in such cartridges keeps its freshness for a long time.
For brewing the coffee powder contained in the cartridge, either manually operated or semi-automatic as well as fully automatic coffee makers are used. Usually, in a manually operated coffee maker, the cartridge is inserted into a cartridge holder that in turn is inserted into the coffee maker. In the semi-automatic coffee makers, the cartridge is inserted into a cartridge retainer or directly into the brewing chamber of the machine, whereby the brewing chamber is manually closed by means of a central lever mechanism. In a fully automatic coffee maker, however, the cartridge is removed from a cartridge magazine and automatically inserted into the brewing chamber; after the brewing operation, the cartridge is removed from the brewing chamber and discarded into a trash receptacle without any intervention of the operator.
All these above mentioned species of coffee maker usually comprise a hollow so-called brewing spike provided with radial outlet openings for injecting brewing water into the cartridge that is also adapted to punch the bottom and the cover, respectively, of the cartridge. Also known are manually operated coffee makers in which the cartridge retainer is provided with a plurality of embossments located on an outlet grate; these embossments break open the cover of the cartridge as soon as brewing water is injected into the cartridge from the opposite side thereof and the cartridge is pressed against the embossments under the influence of the hydraulic overpressure created by the pressurized brewing water. During the subsequent brewing operation, the brewing water is injected into the cartridge by means of the brewing spike, with the result that is flows under pressure through the coffee powder contained in the cartridge and escapes from the cartridge through the opening created by the embossments.
Independent of the fact whether it is a manually operated coffee maker or a semi-automatic or a fully automatic machine, in many cases the coffee maker is designed and adapted to the cartridge so as to produce a coffee beverage having froth on its surface; that froth usually is considered as a characteristic of a good coffee beverage.
Even if great efforts have been taken to ensure that the prepared coffee beverage has durable froth on its surface, in certain countries the desire arises to prepare also conventional coffee in the sense of a filter coffee by means of these coffee makers. In place of the expression “filter coffee”, also the expression “gentle coffee” is used.
In view of such a desire, coffee makers adapted to the cartridge so as to produce a coffee beverage without froth on its surface have been designed (as in co-pending application Ser. No. 11/034,504).
The U.S. Patent document 2003/0172813 discloses a cartridge of the kind referred to herein. It contains a substance extractable by means of water for preparing a beverage, preferably an espresso coffee. Thereby, a sieve-like member is disposed between the bottom of the cartridge and the substance and/or between the cover of the cartridge and the substance, provided with a plurality of axial apertures. The sieve-like member is provided with stampings directed towards the bottom of the cartridge and the cover of the cartridge, respectively, such that fluid channels are formed between the sieve-like member and the bottom of the cartridge, and the sieve-like member and the cover of the cartridge, respectively. In these channels, the brewing water can be distributed over the cross sectional area of the cartridge, and the prepared beverage can be collected in these channels, respectively. In order to prevent that the sieve-like member is punched upon piercing the cartridge, the sieve-like member comprises a central recess directed towards the interior of the cartridge into which the piercing member can extend once the cover or the bottom of the cartridge have been pierced. Even if such a cartridge is well suitable for preparing espresso coffee, it can hardly be used for preparing normal filter coffee, since the cartridge presents a high flow resistance to the brewing water flowing there trough; the result is a formation of froth.
Such known kind of cartridge suffers the drawback that the lower filter can move from its nominal position under the effect of the cartridge's movements, so that coffee powder can flow out together with the beverage by passing between the filter and the lateral wall of the cartridge itself.
The patent document EP 0,326,685 discloses a container, called a brewing chamber, adapted to be disposed of after use, which is collapsible and to the bottom of which a filter bag containing ground coffee or tea is glued. Preferably, the container is made of paper, carton or a similar material. The bottom of the container is provided with an outlet opening located below the filter bag through which the prepared beverage can flow out. In a preferred embodiment of the container, the outlet opening is covered at the outside with a removable foil. Such a container may be usable in a conventional filter coffee machine, but not in an espresso coffee machine.